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if alpha and beta are the roots of the equation 4 x square - 5 x - 1 equals to 0 find the quadratic equation whose roots are two minus alpha coma to minus beta​

User Jarda
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1 Answer

6 votes

Answer:

4x² -11x +5 = 0

Explanation:

Given α and β are roots of 4x² -5x -1 = 0, you want to find the quadratic equation that has (2-α) and (2-β) as its roots.

Factored form

Factoring out the leading coefficient, we can write the factored form of the given quadratic as ...

4(x -α)(x -β) = 0 = 4x² -5x -1

When the roots are changed from α and β to (2-α) and (2-β), the factored form of the new equation is ...

4(x -(2 -α))(x -(2 -β)) = 0

4(x -2 +α)(x -2 +β) = 0

Negating both factors allows us to write this in a familiar form:

4((2 -x) -α)((2 -x) -β) = 0

Comparing to the original factored quadratic, we see that this is the original with x replaced by (2 -x). Then the quadratic we seek is ...

4(2-x)² -5(2 -x) -1 = 0 . . . . . . . . . . . original with x replaced by (2-x)

4(4 -4x +x²) -10 +5x -1 = 0 . . . . simplify a bit

4x² -11x +5 = 0 . . . . . . . . . . simplify

The quadratic whose roots are (2-α) and (2-β) is 4x² -11x +5 = 0.

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Additional comment

Effectively, the roots and the equation are reflected across the line x=1.

if alpha and beta are the roots of the equation 4 x square - 5 x - 1 equals to 0 find-example-1
User Ashok Chandrapal
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3.4k points